Actinide elements halides

By virtue of the fact that the actinide elements constitute a family of elements whose electronic configurations are related to each other in a quite unique way, a comparison of the physical and chemical properties of a series of related compounds has more than the usual interest. In this section some of the more important properties of the actinide element halides are summarized in tabular form, and a number of topics of current interest are described. 

Crystal structure data obtained by X-ray diffraction methods for the actinide element halides are collected in Table IV. Crystal structure determinations have been most important in identifying new compounds of the actinide elements the data are sufficiently extensive now for use in drawing conclusions regarding systematic trends and relations among the actinide elements. The tetrafluorides, for instance, supply one of the best illustrations of an actinide contraction that is entirely similar to the well-known lanthanide contraction (Table V). 

The actinide element halides run the entire gamut of volatility from very high melting and refractory substances such as the trifluorides to the exceedingly volatile hexafluorides. Table VIII lists the actinide element... 

Qualitative Observations on Volatility of Actinide Element Halides... 

Heats and Entropies of Formation of Actinide Element Halide 4... 

Halides of the Actinide Elements Joseph J. Katz and Irving Shefi... 

Margot Becke-Goehring Halides of the Actinide Elements Joseph J. Katz and Irving Sheft Structure of Compounds Containing Chains of Sulfur Atoms Olav Foss... 

Halides, 7 1-26 actinide elements, 2 195-233 anion dependence, 39 139 berkelium, 28 48, 51-53 beryllium, 14 255-332 binary, 35 237-246, 274-280 decomposition, 35 277 dichalcogen dihalides, 35 279-280 equilibrium studies, 35 242 mixed-ligand halides, 35 244-246 reactions, 35 246 selenium halides, 35 240-241... 

In its precipitation reactions ameiicium(IIl) is very similar to the other tripositive actinide elements and to the rare earth elements. Thus the fluonde and the oxalate are insoluble and the phosphate and iodate are only moderately soluble in acid solution, whereas the nitrates, halides, sulfates, sulfides, and perchlorates are all soluble. Americium(VI) can be precipitated with sodium acetate giving crystals isostructural with sodium uranyl acetate,... 

The solubility properties of curium(111) compounds are in every way similar to those of Ihe other tripositive Actinide elements and the tnpositive Lanthanide elements. Thus the fluoride and oxalate tire insoluble in acid soluliun, while the nitrate, halides, sulfate, perchlorate, and sullide are all soluble. 

Thorium forms one series of halides, another one of oxyhalides, and also a series of double or complex halides. In general, stability of these compounds toward heat decreases as die atomic weight of die halogen increases. These compounds are often isostructural with the corresponding compounds of other actinide elements in the (IV) oxidation state. 

Fuger, J., Parker, V.B., Hubbard, W.N., Oetting, F.L., 1983. The chemical thermodynamics of actinide elements and compounds. Part 8. The Actinide Halides. IAEA. 

Most ionic halides dissolve in water to give hydrated metal ions and halide ions. However, the lanthanide and actinide elements in the +3 and +4 oxidation states form fluorides insoluble in water. Fluorides of Li, Ca, Sr, and Ba also are sparingly soluble, the lithium compound being precipitated by ammonium fluoride. Lead gives a sparingly soluble salt PbCIF, which can be used for gravimetric determination of F . The chlorides, bromides, and iodides of Ag1, Cu1, Hg1, and Pbn are also quite insoluble. The solubility through a series of mainly ionic halides of a... 

Progress in the preparative and structural fields of protactinium chemistry has been rapid during the past 6 years and there is now sufficient information available, particularly in the halide and oxide fields, to permit a more balanced comparison than has previously been possible with the properties of the actinide elements, on the one-hand, and those of niobium and tantalum, on the other. In this connection one must, of course, bear in mind the fact that the ionic radii of protactinium in its various valence states [Pa(V), 0.90 A and Pa(IV), 0.96 A] are appreciably larger than those of niobium or tantalum and this itself will have a considerable influence on the chemical and crystallographic properties of the elements. 

Investigations of the solid-state chemistry of the americium oxides have shown that americium has properties typical of the preceding elements uranium, neptunium, and plutonium as well as properties to be expected of a typical actinide element (preferred stability of the valence state 3-j-). As the production of ternary oxides of trivalent plutonium entails considerable difficulties, it may be justified to speak of a discontinuity in the solid-state chemical behavior in the transition from plutonium to americium. A similar discontinuous change in the solid-state chemical behavior is certainly expected in the transition Am Cm. Americium must be attributed an intermediate position among the neighboring elements which is much more pronounced in the reactions of the oxides than in those of the halides or the behavior in aqueous solution. 

During the past few years numerous new penta- and tetravalent protactinium halides and oxyhalides have been characterized, but of the. possible trivalent compounds only Pal3 has been reported. The presently known halides and oxyhalides are compared with those of the other actinide elements in Tables I and II, respectively. It is immediately... 

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